The present invention pertains generally to devices that test integrated circuits, and more particularly to an improved test socket lid assembly which allows easier multi-site usage, improved thermal testing capabilities, and improved failure analysis testing capabilities. The improved socket and lid are easily adaptable for use with either automated testing or hand testing.
Critical integrated circuits are tested before being installed in a finished product. These integrated circuits are frequently incapsulated in ceramic or plastic packages that have contact pads or leads which are electrically connected to the integrated circuit. To test the integrated circuit, it is necessary to make temporary electrical connections to the contact pads or leads on the integrated circuit package. Test sockets created for this purpose are secured to printed circuit boards (load boards) having the appropriate circuitry for testing a particular integrated circuit.
Much of the testing of the integrated circuits may be done with automated equipment. The body of a test socket may be secured to the printed circuit board, and have a plurality of electrical contacts for making electrical connection between the circuitry of the printed circuit board and the contact pads or leads of the integrated circuit. The integrated circuit device is placed into the socket body such that the pads or leads of the integrated circuit contact the electrical contacts of the socket. Typically, the automated equipment which is used to place an integrated circuit into the socket also provides an actuation force against the integrated circuit to engage the integrated circuit pads or leads with the socket electrical contacts.
Automated testing of integrated circuits is not always feasible. This is particularly true when an automated process is not fully developed, or only a relatively small number of integrated circuits are to be tested and the cost of developing a fully automated system is not justified. Hand testing may also be used for special testing purposes, such as integrated circuit characterization tests, failure analysis tests, or thermal testing. In these situations, a lid must be used with the test socket body. The lid takes the place of the automated handling equipment and presses against the top of the integrated circuit to provide the actuation force for engaging the integrated circuit leads with the socket electrical contacts.
Because a user may desire to use a socket body for either automated or hand testing, it is desirable to have a test socket which is adaptable for use either with automated testing or with hand testing. In particular, it is desirable to have a test socket lid assembly which may be attached to a socket body during hand testing of integrated circuits, and which may be removed from the socket body when automated testing is to be done. In addition, it is desirable to have a test socket lid assembly which permits efficient testing of the integrated circuit for tests such as thermal testing, failure analysis, or integrated circuit characterization, as it is these types of tests which are most likely to be performed by hand.
Often, and particularly in automated testing, a user may test more than one device on a single load board. In such a situation, the test socket bodies may be placed side by side, and access to the outer edges of the socket bodies is restricted. In the future, as the automated testing equipment continues to improve and higher densities are possible, this arrangement will be even more common. To avoid interference between adjacent sockets, it would be desirable for all of the socket lid assembly components to be contained within the socket body footprint. Further, it would be desirable if the lid is attachable to the socket body even when the socket body is immediately adjacent another socket body.
As the number of leads or pads of the integrated circuit device increases, the force required to engage the integrated circuit pads or leads to the electrical contacts of the,socket becomes large and a great deal of force must be applied to the top of the integrated circuit. It would be helpful to provide some means of obtaining a mechanical advantage in forcing the integrated circuit device downwardly into contact with the electrical contacts of the test socket. Depending upon the circumstances of the testing environment, it may be favorable to have two separate mechanisms: one for securing the lid in a closed position, and another for providing a mechanical advantage in forcing the integrated circuit towards the electrical contacts. In this manner, xe2x80x9cpinchingxe2x80x9d of the integrated circuit can be avoided, and a true xe2x80x9cverticalxe2x80x9d actuation force may be applied to the integrated circuit.
Failure analysis is often performed by hand on integrated circuit devices. There are two primary methods of failure analysis: mechanical failure analysis and e-beam failure analysis. Both methods require that the top of the integrated circuit, or at least specific portions of the top of the integrated circuit, be removed to expose the conductive traces of the integrated circuit.
In mechanical failure analysis, the integrated circuit is placed in a test socket and a small probe is placed onto a lead trace. The probe is typically a long wire with a bent tip which tapers down to a very small diameter. To properly analyze the integrated circuit, a square tapered hole through the test socket lid assembly is preferred to provide adequate access to the traces. The hole in the test socket lid preferably is nearly as large as the integrated circuit itself to provide maximum access to the traces, while still providing enough downward force on the integrated circuit to provide secure electrical contact with the socket electrical contacts.
E-beam failure analysis places the integrated circuit in a test socket under an electron microscope. In e-beam analysis, maximum viewing access to the top of the integrated circuit is desired. In addition, the top surface of the lid assembly must be flat, without any portions of the socket or lid protruding above the plane of the lid. For these reasons, it is desirable to provide a lid for the test socket body which provides as large of an opening as possible for failure analysis, while still providing enough contact area against the integrated circuit to activate the device within the test socket.
Thermal testing of integrated circuits is important for properly characterizing the integrated circuits. Most thermal tests performed by hand last only a few minutes, although a small portion may last for several hours. Because most thermal tests last for only a short duration, the ability to bring the integrated circuit to operating temperature as quickly as possible is important. Unfortunately, most test socket designs do not provide adequate thermal air flow over the integrated circuit when the integrated circuit is in the test socket. Once the activation force is applied against the integrated circuit to electrically connect it with the load board, efficient thermal air flow is lost, as the pressure plate of the lid tends to block the air flow over the integrated circuit. This uneven flow of air creates hot and cold spots on the integrated circuit surface. As a result, accurate thermal testing of the integrated circuit is difficult or impossible. It is therefore desirable to have a test socket which provides efficient thermal air flow over the integrated circuit while the device is activated in the test socket.
It is thus desirable to provide a test socket assembly which is adaptable with either automated or hand testing, and which has improved capabilities for multi-site usage, as well as thermal and failure analysis testing.
The present invention is a test socket and lid assembly which provides improved multi-site usage, improved failure analysis capabilities, and improved thermal test capabilities. The test socket includes a socket body for making electrical connection between the leads or pads of the integrated circuit and the load board. A lid assembly utilizes a hinge that is removably attached to the socket body allowing the socket to be used with either automated or hand testing. The lid assembly includes a frame member which is pivotally secured to the hinge, with a pressure plate and actuation mechanism retained within the frame member by a cover plate. A latch member holds the lid assembly in a closed position when the test socket is in use. The pressure plate is actuated by the actuation mechanism to move the pressure plate between an unactivated position and an activated position in which the integrated circuit is urged into the socket body. The bottom surface of the pressure plate includes a plurality of channels extending from a central opening in the pressure plate to the circumference of the pressure plate. The channels allow thermal air flow over the integrated circuit for improved thermal performance and improved access to the integrated circuit.
The lid assembly may be attached to or moved from the socket body without the use of tools, even when a plurality of socket bodies are positioned are positioned immediately adjacent one another. In this manner, socket bodies may easily be adapted from automated testing to hand testing when required by the user.
The lid assembly is preferably provided with an actuation member which provides a visual indication to the user when the pressure plate is in an activated position and the enclosed integrated circuit is undergoing testing.